The present invention relates to a source driver, an electro-optical device, an electronic instrument, and the like.
An active matrix type liquid crystal display device includes a plurality of gate lines and a plurality of source lines formed in a matrix. The active matrix type liquid crystal display device also includes a plurality of switching elements, each of which is connected to the corresponding gate line and the corresponding source line, and a plurality of pixel electrodes, each of which is connected to the corresponding switching element. The pixel electrodes are opposite to a common electrode through a liquid crystal (electro-optical substance in a broad sense).
In the liquid crystal display device having such a configuration, a voltage supplied to the source line is applied to the pixel electrode via the switching element which has been turned ON through the selected gate line. The transmissivity of the pixel changes depending on the voltage applied between the pixel electrode and the common electrode.
In a liquid crystal display device, a liquid crystal must be AC-driven in order to prevent deterioration in the liquid crystal. Therefore, polarity inversion drive is performed in the liquid crystal display device in which the polarity of the voltage applied between the pixel electrode and the common electrode is reversed upon expiration of one frame or one or more horizontal scan periods. For example, polarity inversion drive is implemented by changing the voltage supplied to the common electrode in synchronization with the polarity inversion timing.
As technology which reduces the power consumption of a liquid crystal display device which performs polarity inversion drive, a capacitive coupling drive method and similar technology have been known. According to the capacitive coupling drive method, as disclosed in JP-A-2-157815, an image signal voltage is transmitted to a pixel electrode when a thin film transistor (switching element) is turned ON, for example. The potential of the pixel electrode is changed by applying a voltage of which the polarity is reversed when the thin film transistor is turned OFF so that the change in potential and the pixel signal voltage are superimposed on or offset with respect to each other to change the transmittance of the pixel. Power consumption is reduced by reducing the amplitude of the image signal voltage due to movement of a charge caused by the voltage of which the polarity is reversed.
In order to apply the voltage of which the polarity is reversed, it is necessary to provide a switch circuit which switches between the voltages provided in advance. In order to reduce power consumption necessary when controlling the liquid crystal display device, it is indispensable to reduce the impedance of the switch circuit. Therefore, it is necessary to increase the size of a transistor element which forms the switch circuit. However, when the screen size of the liquid crystal display device increases, it is difficult to increase the size of the transistor element which forms the switch circuit provided corresponding to each scan line, for example. Moreover, the image signal write time decreases as the screen size increases. In particular, the image signal write time becomes insufficient when performing multiplex drive. As a result, image quality deteriorates due to occurrence of crosstalk.